Electrodeposition of metals



Patented Nov. 20, 1945 ELECTRODEPOSITION OF METALS Henry Brown, Kansas City, Mo., assignor to The Udylite Corporation, Detroit, Mich., a corporation of Delaware No Drawing. Application February 21, 1941, 'Serial No. 379,951

18 Claims.

My invention relates to improvements in the electrodeposition of metals. It is particularly concerned with the utilization of certain addition agents, for the purposes hereinafter stated, in aqueous acidic electroplating baths.

I have discovered that certain substances, hereinafter described in detail, when added to electroplating baths, particularly aqueous acidic electroplating baths such as used for the electrodeposition of nickel, cobalt, iron, zinc, cadmium, copper, antimony, various alloys containing the aforementioned and other metals,.and the like, are remarkably effective in the prevention of the formation of pits in the electro-deposited coatings, said pits normally being caused by the adherence of gas bubbles during the electrodeposition of the coating. I have found, further, that this result is accomplished despite the fact that very low concentrations of the addition substances are employed and, still further, that these results are accomplished without causing any si g nificantly appreciable interference with the desired appearance, structure and character of the plate.

I have also discovered that the addition agents are highly effective independently of whether various organic or inorganic so-called brightening agents are also present in the electrolyte bath. Various addition agents have heretofore been suggested for reducing or eliminating pitting in electrodeposition operations but, at least in most cases, and apart from other deficiencies which they possess, they have proven to be wholly unsatisfactory where the electrodeposition bath contained brighteners. Thus, for example, in baths employed for the electrodeposition of bright nickel, where the brightening agent comprises an aryl sulphonic acid, for example, naphthalene 1,5 disulphonic acid, sodium salt, or sulphonamides or sulphonimides such as are disclosed in my Patent No. 2,191,813, issued February 27, 1940, various suggested anti-pitting agents have proven entirely unsatisfactory. The use of the addition agents in bright plating baths represents but one aspect of my present invention although, to be sure, a highly important one.

The addition agents which I have found to be unusually satisfactory, in accordance with my present invention, can be used in sufficiently low concentrations so as to reduce substantially, or eliminate entirely, pitting of the deposits and, at the same time, they do not interfere to any significantly appreciable extent with the particular cathodic process involved such as reduction of inorganic or organic substances taking place in the process of electrodepositing the coating. This is highly important where the deposited metal is desired not only free from pits but also of maximun:

ductility and purity and freedom from such inclusions as sulphur, carbon and colloids. It is also of considerable importance in those cases involving bright plating baths, particularly aqueous acid plating baths for the electroplating of nickel, which baths contain brighteners such as those mentioned hereinabove, particularly those wherein the brightener is in the form of a soluble compound containing the radical SO2.N=. As I have pointed out hereinabove, the brightness or brilliance or high luster of the deposits is not adversely affected where the addition agents, to which my present invention relates, are employed.

The novel and highly useful addition agents which accomplish the functions set out hereinabove are, in general, sulphuric acid esters or sulphates of water-soluble polyhydric alcohols partially esterified with aliphatic carboxylic acids, particularly fatty acids, containing from 8 to 18 carbon atoms. Illustrative examples of addition agents which may be utilized in accordance with my invention and in the concentrations which are, in general, preferred. are shown in Table I:

1 Table 1 Anion oil, palm kernel oil, palm oil, olive 011, corn oil, cottonseed oil, sardine oil, tallow, soya bean oil,

Cation (Csprio acid mono-ester of ethylene w s su p ate) a a I cm-(dnbk-c-o-d-d-osmo- (Laurie acid mono-ester of ethylene glycol sulphate) (Myristlc acid mono-ester of ethylene fl D HW) (Higher fatty acid mono-esters of ethylcne glycol sulphate) where 1:10-16 (or mixtures) (Higher fatty acid mono-esters of trimethylene glycol sulphate) where n=8-l6 (or mixtures) mono-sulphate) where n=8-l6 (or mixtures) 11+, NM or metal of both being used...

, The water-soluble aliphatic polyhydric alcohols, the specific esters of which comprise the addition agents of my present invention, may be selected from a large class and include, for example, glycerin; glycols such as ethylene glycol, propylene glycol, trimethylene glycol, and the like; polyglycols such as diethylene glycol, triethylene glycol, and the like; polyglycerols such as digiycerol, triglycerol, tetraglycerol and mixtures thereof carbohydrates and sugars such as dextrose, sucrose,- and maltose; and sugar alcohols such as arabitol, mannitol, sorbitol, dulcitol, mannitan and sorbitan, and the like.

The aliphatic carboxylic acids with which the aforementioned or similar water-soluble aliphatic polyhydric alcohols are esterified may also be selected from a large group including, by

- way of illustration, caprylic acid, nonylic acid,

capric acid, undecylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, ricinoleic acid, mixtures of any two or more of the above-mentioned or other acids; mixed fatty acids, containing from 8 to 18 carbon atoms, derived from animal or vegetable sources as, for example, lard, coconut oil, sesame oil, rapeseed the straight chain, unsubstituted aliphatic carboxylic acids, especially the fatty acids, but, in certain instances, branched-chain and substituted, for example, the alpha-hydroxy derivatives of the aforementioned acids, may, be

utilized. Any of the carboxylic acids listed hereinabove may be esterifled with any of the listed polyhydric alcohols to form partial esters, the sulphates of which comprise the addition agents used in accordance with the present invention.

It will be understood that the sulphuric acid or sulphate radical is linked to the remainder of the molecule of the addition agent through an hydroxy group of the aliphatic polyhydric alcohol radical. The molecule of the addition agent may contain one or more aliphatic or fatty acid radicals and one or more sulphate groups.

Of especial utility are the sulphates of glycerin,

and glycol partial esters of lauric acid or coconut oil mixed fatty acids or special fractions particularly high in content of lauric acid; I prefer to employ, as being unusually satisfactory, monolaurin mono-sulphate, sodium salt, having the formula- CHz-O-SOrNa The addition agents are utilized preferably in the form of their free acids or their alkali metal salts or in the form of a salt of the metal to be electrodeposited. In most cases, it is preferable to utilize the sodium salt.

The addition agents are employed in concentrations of the general order of about 0.05 to about 0.5 gram per liter of electrolyte solution, from about 0.1 to about 0.3 gram per liter of electrolyte solution being most satisfactory in the usual case. More addition agent may be utilized but it is, in general, uneconomic to do so and fully satisfactory results are obtained in practically all cases with the preferred range set out hereinabove.

It will be understood that the addition agents utilized should be soluble in the electrolyte solution at least to such an extent as to fall within the general range as set out hereinabove. In

general, they solubility of the addition agents in the electrolyte solutions decreases with the increase of carbon atoms in the fatty acid chain of the addition agents and, therefore, lower concentrations of such addition agents may be used. Conversely, higher concentrations, generally speaking, of those addition agents should be used where the number of carbon atoms in the fatty acid chain is around 8 or 10 carbon atoms. The addition agents which are preferably employed, as indicated hereinabov, are those derived from fatty acids containing from 10 to 16 carbon atoms and of particular utility are those prepared from fatty acids containing predominantly 12 to 14 carbon atoms, the lauric acid derivatives being especially useful.

Table II sets forth various examples of plating baths with which the addition agents of the present invention may be used efiectively to prevent or inhibit pitting. It will be understood that these examples are merely illustrative and are not to'be taken as limitative of my invention, it being understood that, in general, the novel teachings of my invention may be utilized in connection with plating baths wherein the addition agents are. soluble in the electrolyte solutions to the extent necessary to accomplish the desired results, and wherein said addition agents are not hydrolyzed or otherwise decomposed or modified to an extent sufficient to interfere with their functioning. In general, the addition agents are particularly efiective in aqueous acidic electroplating baths wherein the pH of the bath is of the order of about 2 to Table II In each bath 0.1-0.5 gram/liter or 0.01-0.07 mono-sulphate, sodium Cone Cone, Nickel (bright) MJKL Cobalt Jul.

NlSOaG-IHrO 30-40 CoSOaJHrO NlOlaOHgO 8 CoClaBHaO 8 HiBOa 5 B0: 0 O 1 0.3 (NHI):BO4-- 0 2 ZnSOJHgO 0. l- Temp. foo- F Temp. 70-l20 F D NS-5.5 H-3.5-5.5 Cathode 0. D. 15-75 Cathode C. D 20-200 amp/it. aunt/it.

Nickel-cobalt Conc., Conc., (bright) ozJgal. zinc oz./gal.

NiS0|.6-7Ha0 32 ZnBOaJHzO 30-40 00504.7Ha0 8 ZII(C2H:OI): 4 NlCl2.6HzO 6 Al,(S04), 2 HgBO; 5 HCHO 0.15 Temp. loo-150 Temp. loo-150 pH-4.05.5 nil-405.5 Cathode C. D. 5-100 Cathode C. I). 10-50 amp/ft. ampJlt.

Conc., Conc., Iron ozJgal. Copper oz./gal.

FeCh CuSO4.5HO 30-40 CBCl:.6HgO Cll(CzH 0:)2 Temp. IUD-150 Temp. 70-150" pH-3.55.0 pH=3.0 Cathode C. D. 10-100 Cathod amp/it. amp/ft! While, in the examples listed herelnabove in Table II, I have disclosed the use of the sodium salt of monolaurin monosulphate as the addition agent, it will be understood that others of the addition agents which I have disclosed may be substituted therefor without in any manner departing from the spirit and teachings of my invention.

It will be understood that, from time to time, more addition agent should be added to replenish that which is lost by drag-out or which may possibly be changed, in some manner or other,

during the electrodeposition process.

What I claim as new and desire to protect by Letters Patent of the United States is:

1. In a process of electrodepositing metals, the step which comprises electrolyzing an aqueous acid solution of a salt of the metal to be deposited and a minor proportion of a soluble sulphate of a water-soluble aliphatic polyhydric alcohol partially esterified with a fatty acid containing from 12 to 14 carbon atoms, the metal to be deposited being selected from the group consisting of nickel, cobalt, iron, zinc, cadmium, copper, and antimony.

2. In a process for electrodepositing metals, the step which comprises electrolyzing an aqueous acid solution of a salt of the metal to be deposited and a minor proportion of a soluble sulphate of a member selected from the group consisting of glycerin and glycols, the glycerin and glycols being partially esterified with fatty acids containing predominantly from 12 to 14 carbon atoms, the metal to be deposited being selected from the group consisting of nickel, cobalt, iron, zinc, cadmium, copper, and antimony.

3. In a process for electrodepositing metals, the step which comprises electrolyzing an aqueous acid solution of a salt of the metal to be deposited and a. minor proportion of a soluble sulphate of a mono-ester of a water-soluble glycol with a fatty acid containing from 12 to 14 carbon atoms, the metal to be deposited being selected from the lution also containing a minor proportion of a,

soluble mono-sulphate of a water-soluble aliphatic p lyhydric alcohol partially esterified with a fatty acid containing from 8 to 18 carbon atoms, the sulphate group being linked directly to an hydroxy group of the aliphatic polyhydric alcohol.

5. In a process of electrodepositing nickel, the step which comprises electrolyzing an aqueous acid nickel solution containing a material 'selected from the group consisting of nickel sulphate, nickel chloride, and mixtures thereof, said aqueous solution also containing a minor proportion of monolaurin monosulphate.

6. In a process of electrodepositing metals, the step which comprises electrolyzing an aqueous acid solution-of a salt of the metal to be deposited, said solution containing from about 0.1 to about 0.5 gram per liter of a soluble sulphate of a member selected from the group consisting of glycerin and glycols partially esterifled with fatty acids containing from 8 to 18 carbon atoms, the metal to be deposited being selected from the group consisting of nickel,'cobalt, iron, zinc, cadmium, copper, and antimony.

7. In a process of electrodepositing metals, the step which comprises electrolyzing an aqueous acid solution of a salt of the metal to be deposited, said solution containing from about 0.1 to about 0.5 gram per liter of a soluble sulphate of a member selected from the group consisting of glycerin and glycols partially esterified with fatty acids comprising predominantly lauric acid, the metal of fatty acids comprising predominantly lauric acid, the metal to be deposited being selected from the group consisting of nickel, cobalt, iron, zinc, cadmium, copper, and antimony.

9. A bath for the electrodeposition of metals comprising an aqueous acid solutionof a compound of a metal to be, deposited by electrolysis and a minor proportion of a soluble sulphate of a water-soluble aliphatic polyhydric alcohol partially esterifled with a mixture of fatty acids containing predominantly 12 carbon atoms, the metal to be deposited being selected from the group consisting of nickel, cobalt, iron, zinc, cadmium, copper, and antimony.

10. A bath for the electrodeposition of metals comprising an aqueous acid solution of a compound of a metal to be deposited by electrolysis and from about 0.1 .to about 0.5 gram per liter of a mono-sulphate of a water-soluble aliphatic polyhydric alcohol partially esterifled with a. fatty acid containing from 12 to 14 carbon atoms, the metal to be deposited being selected from the group consisting of nickel, cobalt, iron, zinc, cadmium, copper, and antimony.

11. A bath for the electrodeposition of nickel comprising an aqueous acid solution of a material selected from the group consisting of nickel sulphate, nickel chloride, and mixtures thereof, and a minor proportion of a soluble sulphate of a water-soluble aliphatic polyhydric alcohol partially esteriiied with a fatty acid containing from 8 to 18 carbon atoms, the sulphate group being linked directly to an hydroxy group of the allphatic polyhydric alcohol.

12. A bath for the electrodeposition of nickel comprising an aqueous acid solution of a material selected from the group consisting of nickel sulphate, nickel chloride, and mixtures thereof, and a minor proportion of monolaurin monoculphate.

13. A bath for the electrodeposition of nickel comprising an aqueous acid solution of a material selected from the group consisting of nickel sulphate, nickel chloride, and mixtures thereof, and a minor proportion of a mono-sulphate of a lauric acid mono-ester of a glycol.

14. In a process of electrodepositing metals to obtain bright or lustrous deposits, the step which comprises electrolyzing an aqueous acid solution of a salt of the metal to be deposited and minor proportions of a soluble sulphate of a water-soluble aliphatic polyhydric alcohol partially esterifled with afatty acid containing from 8 to 18 car.

bon atoms, the metal to be deposited being sealso containing-minor proportions of an aryl sul phonic acid brightener and a soluble sulphate of a water-soluble aliphatic polyhydric alcohol partially esterifled with a fatty acid containing from 12 to 14 carbon atoms, the sulphate group being linked directly to an hydroxy group of the all-- phatic polyhydric alcohol.

16. In a process of electrodepositing nickel to obtain a bright or lustrous deposit, the step which comprises electrolyzing an aqueous acid nickel solution containing a metal salt selected from the group consisting of nickel sulphate, nickel chloride, and mixtures thereof, said aqueous solution also containing minor proportions of monolaurin monosulphate and a brightener in the form of a compound soluble in the solution and containing the group -SO2.N=.

1'7. A bath for the electrodeposition of nickel in the form of a bright or lustrous deposit, comprising an aqueous acid solution of a material selected from the group consisting of nickel sulphate, nickel chloride, and mixtures thereof, and minor proportions of an aryl sulphonic acid brightener anda soluble sulphate of a member selected from the group consisting of glycerin and glycols, partially esterified with fatty acids containing from 8 to 18 carbon atoms, the sulphate group being linked directly to an hydroxy group of the glycerin or glycols.

18. A bath for the electrodeposition of nickel in the form of a bright or lustrous deposit, comprising an aqueous acid solution of 'a material selected from the group consisting of nickel sulphate, nickel chloride, and mixtures thereof, and minor proportions of monolaurin monosulphate and a brightener in the form of a compound soluble in the solution and containing the group HENRY BROWN. 

